What is the difference between using an attribute node and texture Coordinate for a UV map?
There isn't really a difference. The attribute node has a few advantages though:


It allows the use of more than one UV map. The texture Coordinate node uses only the UV map with the camera icon selected. 
It Contains the name, which can be useful for organizational purposes.


Note:

Their is also a UV map node coming into cycles, which will eliminate the need for both of theses methods.